Internalizing behaviors are inwardly focused negative feelings, thoughts, and/or actions. Thus, they are not generally observable (as compared to those with externalizing behaviors). Some people who internalize hide their feelings so well that even their families do not notice them. Those with such behaviors often deal with stress by withdrawing from social activities or keeping their feelings inside.
Other examples of internalizing behaviors include not talking, inability to concentrate, sleeping more or less, eating more or less, irritability, anxiety, feeling sad, substance abuse, suicidal thoughts, negative self-talk, feeling unloved, and having illnesses such as head aches and stomach aches which are not physically related. One instance of a worst-case scenario is a seemingly cheerful individual who suddenly commits suicide. Unknown to others, he has been suffering from depression and was only able to express his despair in his journal.